Raised-bed alternatives to pressure-treated wood

Mar. 28, 2013

I learned long ago that pressure-treated wood containing arsenic should not be used to build raised-bed vegetable gardens. All you have to do is a quick internet search for the terms “EPA,” “arsenic,” and “garden” to discover a plethora of advice from researchers studying the impact of using pressure-treated wood in vegetable gardens. Consider this quote from an EPA safety information sheet: “Do not use treated wood under circumstances where the preservative may become a component of food or animal feed. Wear gloves when working with the wood. After working with the wood, and before eating, drinking, toileting, and use of tobacco products, wash exposed areas thoroughly.”

Government officials in Massachusetts warn gardeners, “If you cannot replace raised garden beds with arsenic-free alternatives, peeling root crops or scrubbing with a brush and water helps remove arsenic-contaminated soil that sticks to the vegetables.”

OK. I’m convinced to never use pressure-treated wood around my raised bed garden again. So what are the alternatives?

There are several, but the following are my personal recommendations:

• Untreated lumber that is naturally rot-resistant: These woods include red cedar and black locust. A border of cedar boards is my first choice because it should last for 10 to 12 years before it begins to deteriorate. The price tag on these “specialty woods” might cause you to hesitate, but think of it as a long-term investment in your raised bed garden.

• Untreated lumber for semi-temporary beds: Pine, fir or spruce lumber is suitable for temporary beds (Two to four years). They will, however, need to be replaced periodically. You can make them last a bit longer by coating them with linseed oil, which is extracted from flax seed, inexpensive and is a natural wood preservative.

• Stone or concrete block: Natural stone can be highly attractive, while cinder blocks may be described as “functional” at best. A compromise might be to start with cinder blocks and drive rebar into the ground in the center holes of the initial row. Fill with crushed rock. Flat stones can then be placed on top to provide a natural look.

• Composite lumber: These boards are similar to modern decking boards and are manufactured from a mixture of post-consumer, recycled plastic and natural fibers (rice hulls and wood fiber from a sustainable source).